The present invention relates generally to video transmission systems and, more particularly, to providing and transmitting alternative video data files in place of an interrupted video transmission.
During a video transmission there are often occasions where there is a need to blank the transmission i.e. halt the current transmission of images from the sending side to the receiving side. This may arise, for example, during a video conference where blanking the outgoing video from one party is desirable to keep the receiving party from viewing confidential discussions of the sending party. In the field of video telephony, where limited bandwidth is typically an issue, blanking a video call session or blanking to interrupt a live video transmission may also be desirable when e.g. transferring relatively large files that may take a considerable time to complete. Other examples include blanking the transmission when there is a glitch or technical problem during a video transmission such as during a film broadcast, for example. One straightforward way to perform a blanking operation is to transmit a constant xe2x80x9cblackened-outxe2x80x9d image to the receiving party during the intermission i.e. to simply terminate the transmission. However, a terminated blank image is usually not visually pleasing to view by the receiving party. Thus it would be desirable to display an alternative image during these blanked intermission periods.
Advanced wireless telecommunication services such as those proposed for use with high bit-rate third generation (3G) systems such as Universal Mobile Telephone Service (UMTS) or even lower bit-rate systems such as High Speed Circuit Switched Data (HSCSD) and General Packet Radio Service (GPRS) specified for use with the Global System for Mobile Communications (GSM) wireless standard, will occasionally encounter situations where blanking is necessary during video transmissions. High bandwidth services such as video phone calls, conferencing, simultaneous voice and data services are expected to be supported and will likely place a significant bandwidth load on these systems thereby potentially increasing download times or blanking periods for users of said services. There are a number of existing techniques that can be employed to blank the video in video transmission systems. One very simple but effective technique is to use a mechanical shutter to block the lens of the camera that is transmitting images to the receiver.
FIG. 1a shows a simplified block diagram of the transmitting portion of a basic video telephony system. In the system, an object 100 whose image is to be transmitted is located in front of a camera 110. The light sensitive elements of the camera 110 transform the image into a suitable digitized format that is capable of being stored in a memory 120. In practice, the memory 120 can be a random access memory (RAM) or flash memory, for example, or any suitable medium capable of storing digital data for subsequent retrieval. It should be noted that memory 120 typically functions as an intermediate storage buffer which may not contain a complete image and wherein perhaps only portions of video data from the camera may be briefly stored at any one instant in time. From memory 120, the image data is sent to a video encoder 130 in order to compress the image into a more manageable size. By way of example, an image the size of 38016 bytes or 304128 bits transmitted at 10 frames per second would require a bit rate of 3 Mbit/s. Typical bit rates used in video transmission are in the neighborhood of 50 kbit/s thereby requiring the image to be compressed, which is performed by the encoder by taking advantage of temporal and spatial redundancy and removing the irrelevant information. From the encoder 130, the encoded image data then is sent to a multiplexer 140 which combines the encoded video data and the encoded audio data into a single data stream for transmission.
FIG. 1b shows the video telephony system of FIG. 1a using mechanical shutter means for blanking the image transmission. Presently, many commercial systems use a mechanical shutter 115 to physically block light from the object 100 from reaching the light sensitive elements in camera 110xe2x80x2. This produces the xe2x80x9cblackened-outxe2x80x9d effect which the receiving party sees when the shutter is closed. Typically, the shutter arrangement 115 is integrated into the apparatus of the camera 110xe2x80x2 and works in cooperation with the lens to manually block light from entering the camera 110xe2x80x2.
A disadvantage of using a mechanical shutter solution for blanking in video transmission systems is that it is typically cumbersome to operate and can lead to inaccurate performance i.e. it is often difficult to perform blanking with precise timing of better than {fraction (1/1000)}th of a second with mechanical shutters, for example. Moreover, incorporated mechanical shutters are specially constructed assemblies and cannot be incorporated into many camera constructions. Most importantly, simple mechanical blanking limits the option for providing alternative images which are typically more pleasant to view during the blanking period.
Briefly described and in accordance with an embodiment and related features thereof, in a method aspect there is provided In a video transmission system comprising a camera, a memory for storing electronic images captured from said camera, and a video encoder for encoding said electronic images, a method of transmitting alternative visual data in lieu of a video transmission during an interruption in the video transmission, the method comprising the steps of:
interrupting the video transmission;
transferring said visual data into said video transmission system in response to said interrupted video transmission; and
transmitting said visual data in lieu of said video transmission.
In an system aspect, there is provided a video transmission system comprising camera, a memory for interim storage of digitized images captured from said camera, and a video encoder for encoding said electronic images, wherein a video signal comprising the digitized images from said camera is transmitted to recipient viewers,
characterized in that
the video transmission system is adapted to transmit an alternative video data file for transmission to the viewers in lieu of the video signal that has been interrupted.
In an apparatus aspect, there is provided a wireless handheld device capable of sending and receiving audio and video transmissions for use in making video phone calls comprising:
a camera for capturing images used in connection with said video phone call;
a memory for storing said captured images;
an image generator for producing a generated image for transmission to viewers in lieu of an interrupted video transmission;
an audio encoder for encoding and decoding audio signals associated with said video phone call; and
a video encoder for encoding said captured images associated with said video phone call.